GTreeNode节点下的组件是不是不能通过拓展组件来操作？

private RenderTreeNode(node:CS.FairyGUI.GTreeNode,com:CS.FairyGUI.GComponent)

    {

        let mailData=node.data;

        if(node.isFolder)

        {

            let item=com as mailItem;

            //item.mailTitle.text=mailData.t;

            item.GetChild("mailTitle").asTextField.text=mailData.t;